Heat the oven to 160°C. Line a 20cm x 30cm rectangle baking tin or roasting tray. Add the butter and sugar to a large mixing and use an electric whisk to whip until very light and creamy. You can do this manually, but make sure you whisk until it’s super light!

Add the eggs, one at a time, beating with the whisk after each addition until fully combined. If it looks like it’s splitting at all, add a tbsp of the flour. Add the vanilla extract.

Mix the flour and baking powder together with a pinch of salt, then tip into the egg mixture and use a spatula to combine, you want to make sure it’s all combined but try not to beat out too much air. Add the zest of the lemon, then tip into the baking tin. Bake for 20-25 mins, until risen. To check if it's done, try poking it with a skewer – if it comes out clean, the cake is done. Otherwise, very lightly press the top with your finger, it should spring back to shape when you remove it. Set aside to cool for 5 mins, then flip out onto a drying rack, remove the baking paper and allow to cool. It’s best to ice the underside of the cake as it’ll be flat!

While the cake cools, remove the tops from the strawberries and cut into quarters. Add to a bowl with the raspberries. Dust the icing sugar over the top, stir and set aside.

Once the cake is cool, whip the double cream until thick and creamy. If you lift the whisk up, it should leave a little peak but not too firmly, you want it to be lightly whipped.

Stir the raspberry jam into the strawberry and raspberry mixture, they should have a glossy sauce.

Spoon the cream over the cake, using the back of a spoon to swoosh it over. Top with the strawberries and raspberries. Finish with a dusting of icing and then slice into squares to serve.